The market for electronic devices continually demands increased performance at decreased costs. In order to meet these requirements the components which comprise various electronic devices need to be made more reliable, with more demanding tolerances, decreased sizes, or any combination of these or other factors.
Typically, a semiconductor device includes a semiconductor die with bond pads formed on its surface. The semiconductor die is attached to a lead frame, having a plurality of leads, before bonding. Then, typically, a polymer is dispensed or molded around the die, the leads, and the majority of the lead frame to encapsulate the device. The device is often electrically coupled with a printed circuit board (PCB) by soldering leads of the lead frame to pads on the PCB. The utilization of some encapsulating polymers can lead to performance degradation and damage from electrical shorting, corrosion, or cracking due to moisture. This tends to be an even greater problem when the electronic device must operate in a harsh environment.
Hermetic sealing using a metal or ceramic package provides an increased level of protection. However, the manufacturing process is complex and results in a more expensive package of increased size. Another method that can be utilized is sealing a semiconductor chip's active circuitry at the wafer stage, by applying a passivation coating over the active circuitry on the wafer. However, this process may still lead to a non-hermetically sealed device, by causing damage to the ceramic like coating in the vicinity of the bond pads in subsequent processing, thereby permitting corrosion to deleteriously affect chip reliability and life. Further, this process does not provide protection to the bond pads and electrical interconnections. In addition, these technologies do not lend themselves to all applications. For instance, over the past decade, substantial developments have been made in the micromanipulation of fluids, in fields such as printing technology using inkjet printers. The ability to maintain reliable electrical interconnections in such products has become more difficult as the corrosive nature of the fluids increases.
A fluid ejection device is one type of semiconductor device in which providing robust electrical interconnections to a semiconductor chip operating in a harsh environment is required. There are a wide variety of highly-efficient fluid ejection devices, currently in use, which are capable of dispensing fluid in a rapid and accurate manner. Conventionally, electrical interconnections are made using a flexible circuit that has metal leads that extend out from the flexible substrate and are coupled to bond pads located on the inkjet chip. A polymer encapsulant is dispensed onto the coupled bond pads and beams and is then cured.
In particular, improvements in image quality have led to the use of more complex ink formulations that generally increases the organic content of inkjet inks. The use of such inks, results in a more corrosive environment experienced by the materials coming in contact with these inks. Thus, degradation of the electrical interconnections by these more corrosive inks raises material compatibility issues as well as design issues in order to maintain reliable print heads.
In designing a fluid ejection device, there is a desire to decrease the size of the fluid ejection device, e.g. the size of the silicon die of a print head, increase its reliability, and improving fluid output, e.g. print quality in a print head.